This invention relates generally to a venting system for use in a double-tube xe2x80x9cslip-in-tubexe2x80x9d shaft.
U.S. Pat. No. 6,279,221 (xe2x80x9cthe ""221 patentxe2x80x9d), issued Aug. 28, 2001, for a double-tube xe2x80x9cslip-in-tubexe2x80x9d vehicle shaft, is hereby incorporated in full by this reference. A double-tube xe2x80x9cslip-in-tubexe2x80x9d vehicle shaft includes first and second members each having splined portions. The second member is telescopically positioned within the first member. The splined portion of the first member cooperates with the splined portion of the second member to form the shaft. The cooperating splined portions of the first and second members, however, allow external elements to enter into the double-tube vehicle shaft at the location of the intermeshing splines.
In order to prevent contaminants from entering the shaft, a boot is mounted to the shaft where the second member slips into the first member. The boot may be attached to the first and second members in a substantially airtight configuration, which prevents contaminating particles from entering the shaft.
A slip-in-tube shaft contains, depending on diameter and length, approximately 8 to 16 liters of air sealed inside it during assembly. Shaft working temperature varies continuously depending on ambient temperature, driving conditions, momentary torsional load, and depth and frequency of shaft plunging action. These temperature changes affect the internal air pressure inside the shaft tube. In addition, the air column inside the tube experiences compression and decompression by reversing, at various frequencies, plunging motions of the shaft. Those factors cause, at certain frequencies, the air column inside the tube to vibrate and resonate within the shaft, thereby creating shaft noise and boom, which can degrade driveline noise, vibration, and harshness (NVH) performance. In addition, the air inside the tube can create hydraulic lock and resist manual shaft length adjustment for its installation during vehicle final assembly, which can make the installation of the shaft difficult.